update minimum chrono version to 0.4.20

Author: newAM

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+### Changed
+- Updated minimum `chrono` version to `0.4.20` to satisfy `cargo-audit`.
+
 ## [0.6.1] - 2022-08-01
 ### Fixed
 - Fixed undefined behavior in SPI full duplex RX DMA transfers.

Cargo.lock

@@ -27,7 +27,7 @@ rt = ["stm32wl/rt", "cortex-m-rt"]
 
 [dependencies]
 cfg-if = "1"
-chrono = { version = "0.4", default-features = false, optional = true }
+chrono = { version = "0.4.20", default-features = false, optional = true }
 cortex-m = "0.7.2"
 cortex-m-rt = { version = "0.7", optional = true }
 defmt = { version = "0.3", optional = true }